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[Alan Pevec <1185588@xxxxxxxxxxxxxxxxxx>]

** Changed in: nova/grizzly
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1185588

Title:
  Libvirt pre-Grizzly instances cannot be block migrated

Status in OpenStack Compute (Nova):
  Fix Released
Status in OpenStack Compute (nova) grizzly series:
  Fix Released

Bug description:
  This impacts Grizzly and master.

  Any instances created prior to Grizzly will fail to block migrate.
  Prior to Grizzly, the default image structure was to convert all base
  images to RAW, then resize said image to match that of the selected
  flavor.  Thus, the _base directory would contain <image_hash> and
  <image_hash>_<size_gb>.  From there, QCOW2 files would be created,
  based on the resized backing file.  The entire notion of resized base
  files was eliminated with Grizzly (rightfully so) and with it the code
  which would handle creating these resized backing files.

  The problem is that many environments still have instances created
  with this backing structure.   When utilizing live block migrations
  (nova live-migration --block-migrate), we rely on the destination
  hypervisor to re-populate _base images from Glance.  Therein lies the
  problem, we do not have the code to detect or generate
  <image_hash>_<size_gb> base images.  Thus, the block live migration
  will fail.  The same situation applies if a _base image happens to go
  missing.  We added code in Grizzly to re-download/generate missing
  _base images upon instance reboot, which cannot currently succeed due
  to the same issue.

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